Even adding asp:UpdatePanel or other form of AJAX setup, a postback is still a postback. The page will go through its entire lifecycle on the server as if it were a normal postback without AJAX. The only difference is that with AJAX only a part of the page is sent in the response. Thus, if there are problems with full postback, they will continue to exits with partial postbacks, but will likely be masked by the partial rendering. Thus, I would advise that you make sure the page's logic is OK and add AJAX only then.
As to the error itself - such an exception is usually thrown when there are nested update panels. Here is a simple walkthrough of a problematic case:
- there is an update panel and somewhere in it - another update panel (or AjaxSettings in a RadAjaxManager/RadAjaxManagerProxy, or RadAjaxPanel, it does not matter)
- a postback occurs and response is streamed to the client
- the first update panel in the response disposes its innerHTML and would start replacing it with what the server sent
- the second update panel also attempts to dispose its contents, but since it was already disposed by the first update panel, the MS AJAX scripts cannot find it, so they throw an exception
To avoid this, you should avoid nesting UpdatePanels. If the grid is already in an update panel, you may not need add any more. Also, setting their UpdateMode to Conditional helps because they will dispose more rarely, so if the parent update panel manages to detect the postback comes from the child it may not dispose and cause the error. Thus, this is the second suggestion I can give you.
- look into removing nested update panels as they may not be needed anyway. Perhaps the smallest update panel in ucNotePreview is not needed.
- look into setting UpdateMode to conditional if possible. Try setting it to the update panel in ucNotePreview and to the update panels higher in the hierarchy.
I hope this helps.
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